1908] Chazy Pelf.cypoda 109 



in its marginal outline, with nearly straight, prolonged and 

 terminal umbones; and about one-third longer than high. 



Ventral margin gently convex behind the umbones; hinge 

 line straight and moderately elongated, forming an obtusely 

 subangular junction with the posterior margin, which is some- 

 what obliquely subtruncate above and narrowly rounded below; 

 umbones rather attenuate; beaks small, depressed, incurved. 



Test unknown; surface of casts marked with concentric 

 lines of growth. Hinge dentition and muscular impressions 

 unknown. 



Represented in the collection by eight casts of the interior 

 of single valves. 



A much smaller and more convex species than C. marginalis , 

 Raymond, and with more strongly curved beaks. 



Clionychia (?) GiBBOSA, sp. nov. 



Plate III, figs. 5 and 6. 



Left valve, the only part of the shell known, tumid, strongly 

 convex and gibbous on the umbonal declivity, but flattened 

 obliquely on the anterior side; marginal outline varying from 

 rounded subpentagonal in one specimen (fig. 5) to obliquely 

 subovate in another (fig. 6). 



Anterior margin truncated almost vertically above, and 

 curving abruptly and convexly backward into the narrow and 

 somewhat pointed base below (as in fig. 5); or narrowing 

 rather rapidly and uninterruptedly both inward and downward 

 from the umbo to the base (as in fig. 6). Posterior margin 

 either subtruncated rather obliquely, and nearly parallel with 

 the anterior margin above, and rounding into the base below 

 (as in fig. 5) ; or broadly convex (as in fig. 6) ; hinge line 

 straight and moderately elongated; umbo broad, obtuse and 

 terminal ; its under or inner surface flattened. 



Test unknown; surface of the cast apparently concen- 

 trically striated. Hinge dentition and muscular impressions 

 unknown. 



Represented in the collection by two imperfect and badly 

 preserved casts of the interior of two left valves. The outline 

 of the posterior margin of fig. 6 is a little restored. A peculiar 

 species, whose characters are as yet but very imperfectly 

 indicated. 



